svp important pour demain

1)
A = 24/35 - 3/5  - 9/7
                   2 - 11/4
A = 24/35 - 3 x 7 / 5 x 7 - 9 x 5 / 7 x 5
                      2 x 4 / 1 x 4 - 11/4
A = 24/35 - 21/35 - 45/35
                    8/4 - 11/4
A = 24/35 - 24/35 : - 3/4
A = 24/35 - 24/35 x  - 4/3
A = 24/35 + 72/105
A = 24 x 3 / 35 x 3 + 72/105
A = 72/105 + 72/105
A = 144/105
A = 3 x 48 / 3 x 35
A = 48/35